Process for the direct production of sponge iron particles and liquid crude iron from iron ore in lump form

ABSTRACT

In a process for the direct production of sponge iron particles and liquid crude iron from iron ore in lump form, which is reduced in a direct reduction unit and fed in a hot condition to a melting gasifier, the sponge iron particles which are discharged from the direct reduction unit are separated into a fine grain fraction and a coarse grain fraction, and only the fine grain fraction is fed to the melting gasifier. That ensures economy of operation, without an excess of gas.

DESCRIPTION

The invention relates to a method and apparatus for producing spongeiron particles and liquid crude iron from iron ore in lump form, in adirect reducton unit from which the sponge iron particles are dischargedto a melting gasifier. The term iron ore in lump form is used to denoteiron ore in any lump or piece form, including therefore in the form ofpellets.

A process and an installation of that kind are disclosed in DE-C2-30 34539. In the known process, the operation of melting the sponge ironproduces about 40% more reducing gas than is required for producing thesame amount of sponge iron. In order for the installation to operateeconomically, it is necessarry to have consumers for the excess gas.That means that the installation must be coupled to other installations.However, any coupling of a plurality of installations results in areduction in the availability and viability of the overall installation,and thus results in impaired economy.

Depending on the iron ore used, larger pieces of sponge iron are alsodischarged from the reduction unit and pass rapidly through thefluidised bed of coal in the melting gasifier as such larger pieces ofsponge iron are already moving at high speed when they pass into thequieting chamber in which their speed of downward movement increasesfurther. By virtue of their short residence time in the fluidised bed ofcoal, they experience a correspondingly smaller rise in temperature. Incontrast, small particles of sponge iron have longer residence times inthe fluidised bed, are heated to a higher temperature, and undergofusion more quickly.

The object of the present invention is to provide a process of the kindset forth in the opening part of this specification, which operateseoonomically without an excess of gas and with which the specific outputof the melting gasifier can be increased and the mode of operationthereof can be improved. Another object of this invention is to providean installation for carrying out the process.

The process according to the invention is characterized in that thesponge iron particles discharged from the direct reduction unit areseparated into a fine grained fraction and a cost grain fraction andonly the fine grained fraction is passed to the melting gasifier.

In the process according to the invention, it is not the total amount ofsponge iron particles produced in the direct reduction unit that is fedto the melting gasifier, but only a portion of that amount, so that,when those particles are melted down, a smaller amount of gas isproduced, whereby it is possible to avoid having an excess of reducinggas. The portion of sponge iron particles which is fed to the gasifieris selected insofar as the particle size is limited, in an upwarddirection. That ensures that larger pieces of sponge iron do not passthrough the fluidised bed of coal without being sufficiently heated, andalso ensuring that the fusion zone of the melting gasifier does notsuffer from an accumulation of material which can only be melted byusing an increased amount of energy. The coarse grain fraction which isseparated out on the way from the reduction unit to the melting gasifiercan be fed in a hot condition to a further melting vessel such as anelectric arc furnace, but it can also be subjected to hotbriquetting,passivation or cooling, so as to provide a charge material for asmelting furnace.

As the process according to the invention provides that it is only thefine grain fraction that is melted down in the melting gasifier,difficulties may occur if the melting gasifier is supplied withnon-refined, sulphurrich coal. More specifically, because of the largersurface area of the fine sponge iron particles, with respect to weight,the fine grain fraction binds a greater proportion of the sulphurcontained in the reducing gas, than the coarse grain fraction, so thatthe liquid crude or pig iron which is produced in the melting gasifierhas an undesirably high increase in sulphur content. In that case,additional measures are required in order to reduce the sulphur content;those additional measures, being integrated into the process accordingto the invention, may comprise the following steps, individually or incombination:

1. A desulphurisation agent is fed to the melting gasifier;

2. The proportion of the crude gas produced by the gasification of coal,in the reducing gas, is decreased by admixing a portion of the waste gasfrom the direct reduction unit after a C0₂ scrubbing operation; and

3. The proportion of the fine grain fraction which is melted down in themelting gasifier is reduced in order to make a saving in the meltingheat required, which in turn must be produced by burning coal.

With the step referred to in paragraph 3 above, it is also possible forthe melting gasifier to be supplied with a portion of the waste gas fromthe direct reduction unit as an oxygen carrier, and for a part of thecoal to be gasified by endothermic reactions with the carbon dioxide andthe water vapour in the waste gas.

When the above-mentioned steps are carried out, the reduction in thesulphur content of the sponge iron particles of the fine grain fractionalso causes a substantial reduction in the sulphur content of the spongeiron particles of the coarse grain fraction which are put to useelsewhere, so that, when those sponge iron particles are melted down,there is no longer any need to take particular steps to remove thesulphur therefrom.

If the operation of separating the sponge iron particles into a finegrain fraction and a coarse grain fraction is carried out directly afterdischarge from the direct reduction unit, then the coarse grainseparator must be designed for temperatures of between 700° and 900° C.as the sponge iron particles leave the direct reduction unit at suchtemperatures. In some classification or sorting apparatuses,particularly when using screens, that can give rise to difficulties. Inthat case, it is desirable for the operation of sorting the sponge ironparticles to be carried out only after a cooling operation has beenperformed. Preferably scrubbed and treated waste gas from the directreduction unit is used as the cooling agent, for cooling the sponge ironparticles before they are sorted out. In that case, it is desirable totake steps to ensure that the cooling agent cannot pass into the directreduction unit by way of the sponge iron particle conveyor conduit.

The separated-out sponge iron particles are preferably cooled by meansof cooled, cleaned and treated waste gas from the reduction unit, which,after heat exchange with the sponge iron particles, is admixed with thehot reduction gas flow from the melting gasifier to the reduction unit,for temperature control purposes. That mode of procedure also makeseconomic use of the waste gas from the reduction unit.

The operation of separating out the sponge iron particles of the coarsegrain fraction increases the relative proportion of fine material in thesponge iron which is fed to the melting gasifier, and thus alsoincreases the amount of fine material that may possibly be dischargedfrom the gasifier. Therefore, in accordance with a development of theinvention, the location at which the sponge iron particles are releasedwithin the melting gasifier is displaced downwardly from the top orcover of the vessel, into the vicinity of the upper boundary of thefluidised bed of coal. That is preferably effected by means of a gravityfeed pipe which extends from above into the interior of the meltinggasifier, into the vicinity of the upper boundary of the fluidised coalbed which is formed in the gasifier. In that way, it is also possiblefor the sponge iron particles to be introduced with a deceleratedvertical velocity component, either by providing for suitable changes inthe direction of flow thereof, by the provision of projections disposedin a cascade arrangement in the lower region of the gravity feed pipe,or by the provision of at least one baffle plate underneath the gravityfeed pipe, which is preferably in the form of a truncated cone member,of a similar shape to a Chinese hat.

In order to provide for a metered feed of the sponge iron particles intothe melting gasifier, a discharge means is advantageously providedbetween the coarse grain separator and the melting gasifier, wherein thegravity feed pipe or pipes is or are supplied with sponge iron particlesin a controlled amount by the discharge means. In that way, it is alsopossible to increase the flow resistance in respect of the reducing gaswhich rises up by way of the gravity pipe, and it is possible toeliminate over-heating and sintering of the sponge iron particles in theregion of the coarse grain separator and in the lower portion of thereduction unit.

The invention will be described in greater detail hereinafter by meansof two embodiments with reference to four Figures of drawings in which:

FIG. 1 is a diagrammatic view of a first embodiment of a process andinstallation in accordance with this invention,

FIG. 2 is a view in longitudinal section of the configuration of agravity pipe with liquid cooling,

FIG. 3 is a diagrammataic view of a coarse grain separator, and

FIG. 4 is a diagramatic view of a second embodiment of a process andinstallation in accordance with this invention.

The installation which is shown diagrammatically in FIG. 1, for thedirect production of liquid crude or pig iron from iron ore in lump formincludes a melting gasifier 1 of the kind described in EP-B1-0 010 627.Disposed above the gasifier 1 is a shaft furnace 2 which, according toits mode of operation, can be compared to the upper part of a blastfurnace or a direct reduction shaft furnace. The latter is described inprinciple for example in DE-A-29 35 707. The direct reduction shaftfurnace is fed from above with iron ore in lump form, as indicated by anarrow 3, which moves downwardly in the shaft furnace in the form of aloose fill therein and which is reduced to sponge iron by means of a hotreducing gas which is blown in by way of a central gas inlet 4, at atemperature of about 750° to 900° C. The consumed or expended reducinggas, which is referred to hereinafter as waste gas, leaves the shaftfurnace 2 by way of an upper gas outlet 5.

The hot sponge iron produced by reduction of the iron ore in lump formis discharged from the direct reduction shaft furnace 2 at the bottomthereof, at a temperature of about 750° to 850° C., and passes by way ofa pipe 6 into a coarse grain separator 7. The separator 7 is of theconfiguration that will be described in greater detail hereinafter withreference to FIG. 3. Alternatively, it includes a screen which can besubjected to a thermal loading and which has a mesh size of for example12 mm, by means of which sponge iron particles which are more than 12 mmin size are retained. The sponge iron particles are separated into afine grain fraction and a coarse grain fraction. The sponge ironparticles of the fine grain fraction leave the coarse grain separator 7by way of a first outlet opening 8 and pass by way of a pipe 9 into adischarge means 10 which includes for example a screw or a reamermember. The sponge iron particles of the coarse grain fraction leave thecoarse grain separator 7 through a second outlet opening 11 and pass byway of a pipe 12 to a cooling unit 13 in which they are cooled down toambient temperature so that they can be conveyed, without a serious riskof re-oxidation, to the location at which they are to be processed. Thedischarge of the cooled sponge iron particles from the cooling unit 13is denoted by reference numeral 14.

At its lower end, the discharge means 10 has an outlet opening 16 forthe sponge iron particles, which is in communication with the interiorof the melting gasifier 1 by way of at least one gravity feed pipe 17.The sponge iron particles are discharged in a metered fashion by way ofthe outlet opening 16. In that way, the charge materials which arerequired for charging the melting gasifier are continuously orintermittently fed thereto by way of the gravity pipe 17, in the amountrequired for the melting process in the gasifier. The coal which isrequired to form and maintain the fluidised bed of coal is fed directlyto the melting gasifier 1 by way of a pipe 15.

As described in EP-B1-0 010 627, the melting gasifier, in the operatingcondition thereof, may be subdivided into three portions, namely a lowerportion 18 containing crude iron and slag, a middle portion 19 for thefluidised coal bed and an enlarged upper portion 20 which serves as aquieting or stabilising chamber. In accordance with a development of theinvention, the feed of sponge iron particles into the gasifier 1 doesnot take place at the upper boundary of the quieting claim 20 but withinthe quieting chamber 20, in the vicinity of the upper boundary of thefluidised coal bed 19. In the present case, that is effected by thegravity pipe 17 extending deep into the chamber 20. In that way, it ispossible substantially to reduce the amount of fine grain material whichis discharged from the melting gasifier with the gas and which, in theprocess according to the invention, plays a particular part, in relationto the total amount of sponge iron which is introduced into the meltinggasifier. The best depth to which the pipe 17 extends into the gasifiercan be easily ascertained by experiment. Desirably, the gravity pipe 17terminates just above the upper boundary of the fluidised bed of coal.

The use of one or more gravity pipes 17 also makes it possiblesubstantially to reduce the vertical velocity component of thedownwardly moving material, thereby to increase the residence time ofthe sponge iron particles in the fluidised bed of coal. That reductionin vertical velocity component may be achieved by a direction-changingeffect in respect of the pipes 17 at the lower end, or by the provisionof baffle plates. The high thermal loading on a gravity pipe whichextends into the interior of the melting gasifier means that it isdesirable for the pipe to be cooled. A possible configuration of such agravity pipe is described with reference to FIG. 2.

FIG. 1 also diagrammatically indicates the channels or spouts 21 and 22for tapping off the crude iron and the slag, and also a nozzle or tuyere23 for blowing in an oxygen-bearing gas.

The reducing gas which is produced in the melting gasifier 1 leaves thegasifier 1 by way of the outlet 24 thereof, at a temperature of about1200° C. The gas is passed from there by way of the reducing gas conduit25 to the gas inlet 4 of the direct reduction unit 2. As the reducinggas which is introduced into the direct reduction unit 2 may not exceeda temperature of 900° C, cooling gas which is supplied by way of aconduit 27 is admixed at the location indicated by reference numeral 26,with the hot reducing gas flow which flows upwardly in the conduit 25,for temperature control purposes. The cooling gas is recycled waste gasfrom the direct reduction unit 2 after that gas has been scrubbed andcooled in a waste gas scrubber 28 and the proportion of CO₂ therein hasbeen reduced in a CO₂ absorption tower 29. Although the waste gas, afterhaving been treated in that way, could be mixed in that form with thehot reducing gas from the melting gasifier, for temperature controlpurposes, the embodiment described herein provides that the treatedwaste gas was passed by way of the cooler 13 where it is in direct heatexchange relationship with the sponge iron particles of the coarse grainfraction, to effect cooling of those particles. In that heat exchangeoperation, the treated waste gas is increased in temperature to about500° C. It is then mixed with the hot reducing gas flow in the conduit25, by way of the conduit 27, at the location indicated at 26, in orderthereby to reduce the temperature of the reducing gas flow to a valuebelow 900° C. If more sponge iron than crude iron is to be produced inthe installation, then a part of the treated waste gas must be preheatedin the separate recuperator 31 which is connected in parallel with thecooling unit 13, in order to be able to set the desired bustle pipe gastemperature. The heating gas used should be the untreated waste gas,downstream of the waste gas scrubber 28, the amount of the gas used forthat purpose being dependent on the amount of heat required. Thatarrangement also avoids enriching the recycle gas with inactivecomponents such as N₂.

Reference numeral 30 in FIG. 1 denotes a compressor which is disposedupstream of the CO₂ -absorption tower 29, to produce the pressurerequired. In order to be able to produce sponge iron which has a lowsulphur content, the gas from the melting gasifier 1 must be subjectedto desulphurisation in the hot gas desulphurisation unit 32. For thatpurpose, some cold gas can be added to the gas from the gasifier 1, inorder to adapt the temperature thereof to the desulphurisationoperation.

In order to avoid sintering, the amount of hot gases which pass upwardlythrough the pipes 17, 9 and 6 from the melting gasifier must be keptlow. That can be achieved by virtue of a high flow resistance in theregion of the discharge means 10, the gravity pipe 9 and the coarsegrain separator 7, if the discharge is controlled in such a way that thepipe 9 is always at least partially filled with material. In that way,the resistance in the by-pass path, with respect to the reducing gasconduit 25, will be held at such a high level that there cannot be anyharmful flow of gas through the above-mentioned by-pass duct.

FIG. 2 shows a sectional view of the part of a gravity feed pipe 17which extends into the melting gasifier. Because of the high temperaturein the interior of the melting gasifier, the pipe 17 is provided with aliquid cooling means. For that purpose, three metal pipes 31, 32 and 33which are arranged concentrically with respect to each other, in themanner illustrated in FIG. 2, form a fluid duct through which a coolingfluid, for example water, is passed. The cooling system is covered onall sides with a refractory layer indicated at 34.

The illustrated gravity pipe 17 includes means for producing a change inthe direction of the flow of sponge iron particles flowing downwardlythrough the pipe, thereby to reduce the vertical velocity of theparticles and thus to increase the residence time thereof, by virtue ofthe reduced speed at which the particles go into the fluidised coal bed.For that purpose, disposed in the lower region of the gravity pipe 17are projections 35 which are disposed in a cascade formation and onwhich material can be deposited, thereby to serve as a means for givingprotection from wear. Instead of such projections or in additionthereto, it is also possible for a baffle plate 36 to be provided at thebottom discharge opening of the pipe, the baffle plate preferably beingin the form of a truncated cone member, similarly to a Chinese hat. Thedownwardly moving sponge iron particles are deflected by the projections35 in the pipe so as to follow a meandering path, and the speed ofmovement of the particles in the pipe is also reduced by theprojections, while the baffle plate 36 causes the particles to bedeflected approximately into a horizontal direction, therebyconsiderably reducing their vertical velocity component. Referencenumeral 37 in FIG. 2 denotes the top of the melting gasifier.

The coarse grain separator 7 which is diagrammatically illustrated inFIG. 3 is in the form of an inclined gravity feed channel or chute 38with at least one connecting means or connecting portion 39 whichbranches off downwardly from the channel 38. In the same manner as shownin FIG. 1, the pipe by way of which the sponge iron particles dischargedfrom the direct reduction shaft furnace are fed to the separator 7 isdenoted by reference numeral 6, while reference numeral 8 denotes thefirst outlet opening for the fine grain fraction and reference numeral11 denotes the second outlet opening for the coarse grain fraction.

The loose or bulk material which passes into the coarse grain separator7 from above is naturally separated into the components forming themixture constituting that material, as it passes through the separator7, that is to say, the fine particles settle downwardly and the coarseparticles accumulate on the top. Suitably controlling the flow of spongeiron particles constituting the fine grain fraction, out of the firstoutlet opening 8, produces the flow configuration which is showndiagrammatically in FIG. 3, that is to say, the coarse sponge ironparticles are substantially passed along to the second discharge opening12, by way of the gravity feed pipe 38, and discharged at the opening12. If the flow of fine sponge iron particles out of the separator 7through the connecting portion 39 is controlled, as shown in FIG. 1, bya discharge means 10 which is connected to the coarse grain separator 7by way of a pipe, then the flow resistance in respect of the gas whichrises up out of the melting gasifier can be held at a ccmparatively highlevel, as required.

In the diagrammatic view of a second embodiment of an installation, asshown in FIG. 4, the parts which are the same as in the installationshown in FIG. 1 are denoted by the same references.

A direct reduction unit which is in the form of a direct reduction shaftfurnace 2 is provided at its top with a charging means 3 for the ironore in lump form and a gas outlet 5 for the consumed or expendedreducing gas (waste gas), while at its bottom, it has a controllabledischarge means 41 for the sponge iron particles produced by directreduction from the iron ore, and a gas inlet 4 for hot reducing gas. Themelting gasifier 1 substantially corresponds to the gasifier of thefirst embodiment. In this embodiment however, the top or cover of theupper portion 20, which serves as a quieting or stabilising chamber, hasa chamber which is referred to as the gasifier head portion 42 and whichcommunicates with the quieting chamber 20. The gasifier head portion 42has a gas outlet 43 for the reducing gas (crude gas) which is producedin the melting gasifier, a gas inlet 44 for scrubbed and treated wastegas from the direct reduction shaft furnace, and an inlet 45 for adesulphurisation agent. The pipe 15 for the coal feed and the dip pipe17 for the introduction of the fine grain fraction are also passedthrough the top of the melting gasifier.

Provided in the lower portion of the melting gasifier are outlets 21 forliquid crude iron and 22 for liquid slag, while disposed above the slaglevel is at least one tuyere 23 or at least one blowpipe or burner 23afor blowing in gases and fine-grain solid materials.

Disposed underneath the direct reduction shaft furnace 2 is a coolingunit 13a for the hot sponge iron particles which are discharged throughthe discharge means 41. The intake opening 46 of the cooling unit 13afor the hot sponge iron particles communicates with the discharge means41 through the gravity feed conduit 6. Associated with the gravity feedconduit 6 is a level measuring means 47 for controlling the dischargemeans 41.

In its upper region, besides the intake opening 46 for the hot spongeiron particles, the cooling unit 13a also has an outlet 48 for thecooling gas while in its lower region, besides an outlet opening 14 forthe cooled sponge iron particles, the cooling unit 13a has an inlet 49for the cooling gas. As in the embodiment described with reference toFIG. 1, the cooling action takes place in a counter-flow mode and indirect heat exchange relationship with the sponge iron particles whichare moving downwardly in the cooling unit. As the cooling unit 13a isnot only fed with the coarse grain fraction of the sponge ironparticles, as in the embodiment shown in FIG. 1, it is desirable for thecooling unit to be provided in its upper region with a quieting chamberin order to minimise the amount of fine components discharged therefrom.That can be effected for example by the gravity feed pipe 6 beingextended by a given length into the cooling unit so that a quietingchamber is formed above the cone-shaped surface of the material withinthe cooling unit.

Disposed below the cooling unit and connected to the outlet opening 14thereof by means of a further gravity pipe 48 is a classification orsorting means 7a which is in the form of a screening station and whichprovides for separation of the sponge iron particles into a fine grainfraction and a coarse grain fraction. The outlet opening 8 for the finegrain fraction is connected by the conduit 9 to the fine grain ccntainer10 which is disposed above the melting gasifier and which has an outletopening 16 communicating with the dip pipe 17. As an alternative or inaddition, it is possible to provide a connection to the pipe 15 by wayof which the coal is introduced into the melting gasifier. If, due tothe shortage of available space, the sorting means 7a is not arrangedabove the melting gasifier 1 and the conduit 9 cannot be in the form ofa gravity feed conduit, then suitable conveyor means for conveying thefine grain fraction are to be provided in the conduit. If the separationoperation in the sorting means 7a is performed in such a way that thefine grain fraction only contains portions with a grain size of up to 3mm, then it may be desirable for at least a part of that fraction to beblown into the melting gasifier by way of the nozzles or tuyeres 23 or23a respectively. Suitable conduits are then to be provided, for thenozzles or tuyeres.

Connected to the outlet opening 11 of the sorting means 7a for thecoarse grain fraction which is separated out of the process is a conduit12 for feeding the coarse grain fraction to a separate melting unit or ameans for compacting or passivation or a further cooling unit 13, asshown in FIG. 1, to which treated waste gas is supplied, as the coolingagent.

As in the case of the embodiment described with reference to FIG. 1, awaste gas scrubber 28 is connected to the waste gas outlet 5 of thedirect reductionshaft furnace and the gas outlet 51 of the waste gasscrubber 28 communicates by way of conduits 52 and 53 with a CO₂-absorption tower 29 having a gas outlet 54 which is connected by way ofconduits 55 and 56 to the inlet 49 of the cooling unit 13a for thecooling gas. In addition, as in the first embodiment, the arrangementincludes a conduit 27 from the gas outlet 48 of the cooling unit 13a tothe reducing gas conduit 25, in order to mix treated waste gas which hasbeen heated in the cooling unit 13a, with the reducing gas flow which ispassed by way of the conduit 25 to the gas inlet 4 of the directreduction shaft furnace 2. That arrangement not only provides fortemperature control of the reducing gas which is fed to the directreduction shaft furnace 2, but it is also possible for the consumptionof coal and oxygen in the melting gasifier to be reduced to almost half.That also reduces to almost half, the amount of sulphur which isintroduced with coal and the sulphur content in the reducing gas.

Supplementary to the installation shown in FIG. 1, the installationshown in FIG. 4 also includes the following pieces of equipment andconnecting conduits.

Associated with the cooling unit 13a is a cooling gas circuit 57 whichincludes a conduit 56, with a cooling gas scrubber 58 and a compressor30a. That arrangement takes account of the fact that the coolingoperation in the cooling unit requires a larger amount of cooling gasthan the available amount of treated waste gas which is supplied by wayof the conduit 55.

From the conduit 27 which connects to the gas outlet 48 of the coolingunit or the cooling gas circuit 57, a conduit 59 branches off to theinlet 44 in the gasifier head portion 42. A connecting conduit 60,connecting to the gas outlet 54 of the CO₂ -absorption tower 29,ccmmunicates with the conduit 59. Treated waste gas at differenttemperatures can be fed to the gasifier head portion 42 by way of theconduit 59 so that in this case the temperature can be adjusted to theoptimum temperature for the hot gas desulphurisation operation.

The outlet 43 in the gasifier head portion 42 for the reducing gas whichis produced in the melting gasifier 1 is connected by way of a conduit61 to a cyclone 62; connected to the gas outlet 63 of the cyclone 62 isthe reducing gas conduit 25 which leads to the direct reduction unit.Instead of a cyclone, it is also possible to use a plurality of cycloneswhich are connected together to form a cyclone battery. The outletopening 64 for the solid materials which are separated out communicatesby way of a conduit 65 with a conduit 66 which is connected by way of acompressor 30 to the gas outlet 51 of the waste gas scrubber 28. Theconduit 66 carries a portion of the waste gas leaving the waste gasscrubber 28 to the burner or blowpipe 23a, as oxygen-bearing gas, thatgas also serving as a carrier gas for the solid materials which areseparated out in the cyclone 62. Oxygen can be fed to the burner 23a orthe tuyeres 23 by way of a conduit 67. A branch conduit 68 goes from theconduit 52 which is connected to the gas outlet 51 of the waste gasscrubber 28, to a steam generator 69. Therefore, a part of thenon-treated waste gas can be used as a heating gas for producing steamwhich is required in the CO₂ -absorption tower 29.

Besides the requirement of avoiding an excess amount of reducing gaswhich is produced in the melting gasifier 1, the process when carriedout with the installation shown in FIG. 4 also takes account in aparticularly economical manner of the requirement that the sulphurcontent of the crude iron which is melted in the gasifier and in thecoarse grain fraction of the sponge iron particles, which are separatedout of the process, should be kept at a low level, if the energy carrierused in the process is coal which has a high sulphur content. For thatpurpose, means are provided for reducing the amount of energy requiredfor melting the fine grain fraction in the melting gasifier and forfeeding the process with the waste gas from the direct reduction unit,partly in an untreated condition and partly after a CO₂ scrubbingoperation and after direct heat exchange in the cooling unit for thesponge iron particles which are discharged from the direct reductionunit.

The amount of energy which is required for producing the melting heatand which is to be produced by burning coal is reduced by virtue of thefact that, in the operation of separating the sponge iron particles inthe classification or sorting means 7a, the proportion of the fine grainfraction relative to the coarse grain fraction is reduced, that is tosay, the grain band of the fine grain fraction which is fed to themelting gasifier 1 is reduced to particles of up to 5 mm and preferably3 mm in size. Because of the longer residence time in the fluidised bedof the melting gasifier, those particles can be melted down with asubstantially smaller amount of energy, that is to say therefore with asmaller amount of coal and therefore a smaller amount of sulphur. It isthen also possible for a part of the untreated waste gas which issupplied by the waste gas scrubber 28 and which contains carbon dioxideand water vapour, to be used for gasification of the coal. In theembodiment shown in FIG. 4, a part of the waste gas is fed by way of theconduit 66 to one or more burners or blowpipes 23a of the meltinggasifier 1, which open into the fluidised bed of coal. Using the wastegas as a carrier gas, the discharge from the cyclone 62, namelydesulphurisation agent and coal particles which are separated out of thereducing gas, is also recycled to the melting gasifier. In order toprotect the injection opening from slagging or slag corrosion, theburner 23a is supplied with oxygen or air as a combustion agent, by wayof the conduit 67, and a part of the waste gas or the waste gas-dustmixture is burnt. The amount of waste gas which is supplied by way ofthe conduit 66 should be so adjusted that the gasifier head portiontemperature, in connection with other temperature control arrangements,is between 850° and 1250° C., preferably 1100° C. It will be appreciatedthat the possibility of using waste gas as an oxygen carrier forcarrying out the gasification operation also permits the consumption ofoxygen per tonne of product to be reduced, thereby increasing theeconomy of the process.

A further saving of coal and thus a further reduction in the sulphurcontent in the reducing gas and in the sponge iron may be achieved bywaste gas which is treated in the CO₂ absorption tower being mixed withthe reducing gas. In the process carried out with the installation shownin FIG. 4, that is effected by a part of the waste gas which is treatedin the CO₂ -absorption tower 29 being passed by way of the conduits 55and 56 through the cooling unit 13a, with that part being heated indirect contact with the hot sponge iron particles, and a portion thereofthen being passed to the reducing gas conduit 25 and a further partbeing passed to the gasifier head portion 42 by way of the conduit 59.The other part of the treated waste gas which is supplied by the CO₂absorption tower 29 is fed directly to the gasifier head portion 42 byway of the conduit 60 and a part of the conduit 59. The amount oftreated waste gas which is mixed with the reducing gas permits theconsumption of coal and oxygen and thus also the amount of sulphurintroduced with the coal and the sulphur content in the reducing gas, tobe reduced to about half.

The treated waste gas which is supplied to the gasifier head portion 42by way of the conduit 59 also provides for temperature control, whereinthe temperature in the conduit 59 can be determined by the proportionsof the amounts supplied by way of the conduit 27 and by way of theconduit 60. Temperature adjustment in the gasifier head portion isessential particularly when a desulphurisation agent is supplied to thegasifier head portion or the exhaust gas conduit 61 in order further toreduce the sulphur content in the reducing gas. The optimum temperaturefor hot gas desulphurisation is about 900° C. In the method described,the gasifier head portion 42 is supplied by way of an opening 45 with adesulphurisation agent such as calcium hydroxide in fine-grain form, andthe optimum temperature for the hot gas desulphurisation operation isadjusted by the treated waste gas which is blown in through the gasinlet 44. Desulphurisation of the reducing gas is essentially effectedin the gasifier head portion and in the exhaust gas conduit 61. Expendeddesulphurisation agent and desulphurisation agent which has not yet beenexpended are separated out in the cyclone 62 and recycled to the meltinggasifier by way of the conduit 65.

The above-specified steps also make it possible, when using sulphur-richcoal, to reduce the sulphur content of the sponge iron particles to suchan extent that the coarse grain fraction which is separated off can beprocessed in a steel works without further operations for removal ofsulphur therefrom. The fine grain fraction which, for the above-statedreasons, has a substantially higher sulphur content than the coarsegrain fraction--because the fine sponge iron particles have a largersurface area, in relation to weight, such particles bind a larger amountof sulphur--, is at least partially desulphurised by thedesulphurisation agent which is supplied to the melting gasifier, andseparated out bound to the desulphurisation agent by the slag.

I claim:
 1. In a process for the direct production of sponge ironparticles and liquid crude iron from iron ore in lump form, wherein theiron ore is reduced to sponge iron particles in a direction reductionmeans by a hot reducing gas, and sponge iron particles which aredischarged from the direct reduction means are fed to a melting gasifierin which the heat required for melting the sponge iron, and reducinggas, are produced from coal which is introduced into the meltinggasifier and oxygen-bearing gas is blown thereinto, at least a part ofthe reducing gas, after cooling to a temperature necessary for reductionbeing passed into the reduction zone of the direct reduction means, theimprovement comprising separating the sponge iron particles which aredischarged from the direct reduction means into a fine grain fractionand a coarse grain fraction and passing only the fine grain fraction tothe melting gasifier.
 2. A process according to claim 1 wherein the finegrain fraction contains particles of up to 20 mm in size.
 3. A processaccording to claim 2 wherein the fine grain fraction contains particlesof up to 12 mm in size.
 4. A process according to claim 1 wherein theupper limit of the particle size of the fine grain fraction is soselected that the amount of reducing gas which is produced when thesponge iron particles are melted down in the gasifier aproximatelycorresponds to the amount required for the process of reducing the ironore in the direct reduction means.
 5. A process according to one ofclaims 1 to 4 wherein the sponge iron particles of the fine grainfraction are introduced adjacent to the upper boundary of a fluidisedbed which is formed in the melting gasifier, at a retarded verticalvelocity.
 6. A process according to claim 5 wherein the sponge ironparticles are supplied through at least one pipe.
 7. A process accordingto claim 1, wherein the separation between the fine grain fraction andthe coarse grain fraction is so selected that the mean sulphur contentof the fine grain fraction corresponds at least to five times the meansulphur content of the coarse grain fraction.
 8. A process according toclaim 7 wherein the mean sulphur content of the fine grain fractioncorresponds at least to ten times the mean sulphur content of the coarsegrain fraction.
 9. A process according to claim 7 wherein the grainfraction substantially contains particles of up to 5 mm in size.
 10. Aprocess according to claim 9 wherein the fine grain fractionsubstantially contains particles of up to 3 mm in size.
 11. A processaccording to claim 1, wherein a desulphurisation agent is added to thereducing gas which is produced in the melting gasifier.
 12. A processaccording to claim 11 wherein the desulphurisation agent is blown intoan exhaust gas conduit of the melting gasifier for producing reductiongas.
 13. A process according to claim 12, wherein a part of waste gasfrom the direct reduction means is admixed with a reducing gas producedin the melting gasifier, after said waste gas has been scrubbed andcooled in a waste gas scrubber and treated by the removal of CO₂.
 14. Aprocess according to claim 13 wherein at least a part of the washed andtreated waste gas is heated in direct heat exchange relationship withsponge iron particles which are discharged from the direct reductionmeans before the waste gas is mixed with the reducing gas.
 15. A processaccording to claim 13 wherein the so treated waste gas is blown into thehead end of the melting gasifier.
 16. A process according to claim 13,wherein the so treated waste gas is blown into the reducing gas conduitfrom the melting gasifier to the direct reduction means.
 17. A processaccording to claim 14, wherein direct heat exchange of the scrubbed andtreated waste gas with the sponge iron particles is effected in acoooling unit, the hot sponge iron particles which are discharged fromthe direct reduction unit being conveyed into the cooling unit by way ofa gravity feed pipe.
 18. A process according to claim 17 wherein thesponge iron particles are separated into a fine grain fraction and acoarse grain fraction after direct heat exchange with the treated wastegas.
 19. A process according to claim 18, wherein the sponge ironparticles of the coarse grain fraction are cooled by cooled, cleaned andtreated waste gas from the direct reduction means.
 20. A processaccording to claim 19, wherein a part of the waste gas from the directreduction means, after scrubbing and cooling in a waste gas scrubber, isfed to the melting gasifier as a gasification agent.
 21. A processaccording to claim 20 wherein a fluidised bed is formed in the meltinggasifier and the waste gas is blown into the fluidised bed.
 22. Aprocess according claim 1, wherein the reducing gas produced in themelting gasifier is treated to remove dust therefrom in at least onecyclone separator before it is fed to the direct reduction means and atleast a part of the particles which are separated from in the cycloneseparator and which are discharged therefrom are recycled to the meltinggasifier.
 23. A process according to claim 22 wherein the cyclonedischarge, with the waste gas as a conveyor gas, is blown into themelting gasifier.
 24. A process according to claim 23 wherein thecyclone discharge is blown into the melting gasifier with the waste gasafter admixing with oxygen or air, by way of at least one blowpipe.